Electronic system



Dec. 13, 1966 N. T. NEAPOLITAKIS 3,291,109

ELECTRONIC SYSTEM Filed Aug. 10, 1964 FIG. 1

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N/CHOL/LS Z' NEAPOL/TAK/S mm (Lu, K Mek United States Patent 3,291,109ELECTRONI SYSTEM Nicholas T. Neapolitakis, Chicago, Ill., assignor toMotorola, Inc., Franklin Park, Ill., a corporation of Illinois FiledAug. 10, 1964, Ser. No. 388,640 4 Claims. (Cl. 123-148) This inventionrelates generally to ignition systems for internal combustion enginesand more particularly to an improved ignition system utilizing anencapsulated magnetically actuated reed switch and a switching circuitincluding semiconductor devices.

Internal combustion engines, as used in automobiles and other vehicles,include an ignition system for firing the combustible charges in thecylinders thereof. Such systems are controlled by a switching mechanism,usually referred to as breaker points, which operates in synchronismwith the engine. The breaker points are connected in a circuit andactuate the same to provide high voltage pulses, and these are appliedto the various spark plugs or other ignition devices in the cylinders ofthe engine through a distributor device. The distributor device alsooperates in synchronism with the engine to apply the pulses toparticular cylinders. In systems commonly in use wherein the breakerpoints interrupt the current supplied to the primary of an ignitioncoil, it is necessary for the breaker points to interrupt a currentsufficiently large that arcing and pitting takes place at the contacts.This results in poor operation after a period of time, and the pointsmust be replaced at regular intervals. This results in objectionablemaintenance of the engines.

In order to reduce the current through the breaker points, ignitionsystems have been used including transistors for interrupting thecurrent supplied to the ignition coil. A smaller current for triggeringthe transistor circuit is then switched by the breaker points. Thesesystems have reduced the wear at the breaker points but have not beenentirely satisfactory as faulty operation may still take place when thebreaker point contacts are contaminated by foreign particles. Themechanical cam structure and the breaker point rubbing block, foractuating the breaker points, wear and must be periodically adjusted forproper dwell time. Further the switching action in the breaker points,particularly at low speeds such as during starting, has not provided thedesired action in the ignition system.

It is, therefore, an object of this invention to provide an improvedignition system for an internal combustion engine which is reliable inoperation and requires a minimum of maintenance.

Another object of the invention is to provide a transistorized ignitionswitch system including a switching device which provides extremelyrapid switching action.

A feature of the invention is the provision of an ignition system for aninternal combustion engine including a circuit switched by anencapsulated magnetic reed device, with a magnetic circuit thereforwhich provides rapid reversal of the magnetic field through the reed,and rapid switching action thereof.

Another feature of the invention is the provision of a transistorignition system controlled by a reed device positioned in a magneticcircuit having a rotating magnetic member and pole pieces cooperatingtherewith so that the flux through the reed device changes sharply andreverses to provide rapid switching action. The rotating member may be adisc of magnetic material with discrete radial poles, or an axiallymagnetized disc with pole "ice plates on the opposite faces thereofhaving interleaved pole pieces to provide alternate poles about theperiphery. The reed device includes encapsulated magnetic contactshaving portion extending therefrom and engaging pole pieces throughwhich the reed device is intermittently coupled to poles of oppositepolarity of the rotating member. The magnetic reed may be positionedhorizontally, vertically, or at an angle, to provide the desired actionin the space which may be available.

The invention is illustrated in the drawings wherein:

FIG. 1 is a circuit diagram of the ignition system of the invention;

FIG. 2 is a cross sectional view showing the magnetic structure in adistributor housing;

FIG. 3 illustrates an alternate magnetic structure for the system ofFIG. 1;

FIG. 4 is a cross sectional view along the line 4-4 of FIG. 3;

FIG. 5 shows the sealed reed device and the coupling to the magneticpole; and

FIG. 6 shows an alternate embodiment with the reed device positionedvertically.

In practicing the invention, an ignition system is provided whichincludes an ignition coli, and one or more switching transistorsconnected in series with the coil across a source of potential forinterrupting the current through the coil to produce firing pulses. Theconduction of the switching transistor (or transistors) is determined bya magnetically actuable encapsulated reed switch which is placedadjacent a rotating magnetic structure, and which may be provided in adistributor housing. The rotating magnetic structure produces afluctuating field which opens and closes the reed switch in synchronismwith the internal combustion engine to provide properly timed firingpulses. The rotating magnetic 'structure includes discrete poles whichmove past pole pieces of amagnetic structure including the reed device.This causes abrupt changes in the reluctance so that the flux throughthe reed device changes quite sharply. The alternate poles are ofopposite polarity so that the flux through the reed device reverses andthis acts to provide positive movement of the reeds so that extremelyrapid switching action takes place. The rotating magnetic structure maybe a toothed wheel with alternate teeth magnetized to oppositepolarities, or may be an axially magnetized disc with pole plates oneither side having teeth extending therefrom and interleaved with eachother to provide alternatepoles of opposite polarity. The reed switchmay be positioned in various manners as may be required to meet spacerequirements.

Referring now more particularly to FIG. 1, there is shown an ignitionsystem for an internal combustion engine 11 having eight cylinders.Engine 11 has a plurality of spark plugs 12 for igniting the fuelmixture in the cylinders thereof. High voltage firing pulses aresupplied to spark plugs 12 by a distributor 13 which has a plurality offixed contacts 14 connected to respective ones of spark plugs 12. Thehigh voltage pulse is developed in the secondary winding of a highvoltage ignition coil 16, and applied to the moving contact 15 whichmoves into proximity with the fixed contacts 14.

As shown in FIG. 1, ignition coil 16 is of the well knownauto-transformer type. However, a double winding transformer may also beused within the scope of the invention. When current flowing through theprimary of ignition coil 16 is suddenly interrupted, a high voltagespike will be induced in the secondary thereof. It is this spike that isapplied to moving contact 15 of distributor 13, and from the fixedcontacts 14 thereof to the spark Ca plugs 12 of internal combustionengine 11. The primary of ignition coil 16 is connected to the source ofcurrent, namely storage battery 17, by a pair of transistors 18 and 19.Battery 17 may be charged by an alternator or generator 21, the outputof which may be regulated by regulator 23 in a well known manner. Alsoconnected in series with the primary of coil 16 and transistors 18 and19, are ignition switch 25 and ballast resistor 27.

As previously stated, transistors 18 and 19 control the conduction ofcurrent to the primary of ignition coil 16. Upon interruption of currentin coil 16, a high reverse voltage occurs. Zener diodes 28 and 29 areconnected across the emitter and collector portions of transistors 18and 19 respectively to prevent the reverse voltage across these portionsfrom exceeding their breakdown voltage. A resistor 31 is connectedbetween the emitter and base portions of transistor 18, and the baseportion of transistor 18 is connected through an isolating diode 33 toresistor 35. Resistor 37 connects the base portion of transistor 19 toits emitter portion, and the base portion is also connected to resistor36. A control transistor 41 V has its emitter portion connected to thejunction between resistors 36 and 35, and has its collector portiongrounded.

Upon conduction of transistor 41, transistor 19 will be forward biasedthrough resistor 36, whereas transistor 18 will be forward biasedthrough resistor and diode 33. This will cause current to flow in coil16. When transistor 41 is cut otf, the potential on the base portions ofboth transistors 19 and 18 will rise quickly toward their respectiveemitter potentials due to the connection through resistor 37 and 31,cutting these transistors off. This interrupts current through coil 16producing a firing pulse therein.

The conduction of control transistor 41 is controlled by a circuitresponsive to the speed and timing of engine 11. A resistor 43 connectsthe base portion of transistor 41 to battery 17 through ignition switch25. The base portion of transistor 41 is also connected to groundthrough resistor 44 and magnetically actuable reed switch 45. Resistor44 may be very small and can have a value as low as 1 ohm. This protectsthe reed from excessive current in the event that the collector portionof transistor 41 is not well grounded. Resistor 44 also reduces thecurrent spike through the reed contacts when the reeds close initiallyas the system starts. This is because at this time v the voltage appliedthrough resistors 37 and 36 to the emitter portion of transistor 41 isalmost the full supply voltage because of the inductance of coil 16.

Reed switch 45 comprises a pair of reeds 47 and 48 which are normallyopen. Reed switch 45 is encapsulated and placed adjacent a rotatingmagnet member 50 which, during the course of its rotation, will alignpoles 51 of op posite polarity adjacent to pole pieces 52 and 53 whichare magnetically connected to reeds 47 and 48 respectively. This causesthe reeds to attract one another and therefore to close. The discretepoles 51 are shaped to match the pole pieces 52 and 53 so that as thepoles move into and out of registry with the pole pieces a sudden changein flux takes place. This provides a fast snap switch action.

The alternate poles marked N, S, N, etc. around the periphery of theannular magnet 50 are uniformly spaced to operate the reed switch atregular angular positions of the magnet. As the magnet 50 continuesrotation, the alternate polesproduce fields which are in oppositedirections to open the reeds at the half way point and then close themagain once the field is completely reversed. It should be noted that thefield may actually force the reeds apart in the event that they tend tostick together due to magnetic retentivity, moisture, or foreignparticles.

With reed switch 45 closed, the base portion of transistor 41 will begrounded and hence transistor 41 will be driven into conduction toground the juncture between resistors 36 and 35. This causes thetransistors 18 and 19 to conduct and current to flow through coil 16.When reed switch 45 opens, the base portion of transistor 41, which isconnected to battery 17 through resistor 43, will rise to batterypotential, actually reverse biasing the transistor 41 to insure rapidcut off. This cuts ofl transistors 18 and 19 and interrupts currentthrough coil 16 so that a high voltage is developed thereacross. This isapplied through distributor 13 to the spark plugs 12, as previouslydescribed.

Magnetically actuable reed switches of the type suitable for use asswitch 45 are commercially available. One source for such switches isHamlin, Inc. of Lake Mills, Wisconsin, and the switches are designatedMRR-Z. The reeds are glass encapsulated in a tube which may be approximately Vs of an inch in diameter and less than 1 inch long. Thereeds may be made of nickel'iron alloy and rhodium plated. Other contactstructures may be used, such as gold diffused or nickel plated contacts.Suitable reed switches are also available from other sources.

As the reed switch and the magnetic poles connected thereto will besupported by insulated members it is not necessary that either of thereeds be grounded as shown in the circuit of FIG. 1. This provides fulllatitude of use of ignition systems in various circuit arrangements invehicles having either the positive or the negative terminal of theelectrical supply grounded.

In FIG. 2 the reed switch and magnetic structure are shown in adistributor housing with the distributor switch 13. The distributorhousing includes a base 71 and a cover or cap 72. The distributor shaft'73 extends upwardly into the housing and actuates drive plate 75. Driveplate 75 is connected through the spring biased fiy weight mechanism 77and drive pin 78 to the centrifugal advance plate 79. Advance plate 79drives rotor shaft 81 on which insulating rotor 83 is mounted. Rotor 83carries the moving contact 15 of the distributor, which was described inconnection with FIG. 1. The fixed contacts 14 of the distributor, whichare connected to the spark plugs, are mounted in the cap 72 and extenddown wardly therefrom. The moving contact 15 engages a cen= ter contact60 which is connected to ignition coil 16, to complete the circuittherefrom to one of the fixed contacts 14.

The rotating magnetic member 50 may be mounted on the rotor shaft 81,which in the standard distributor structure carries a cam for operatingmechanical breaker points. The encapsulated reed switch 45 is placedadjacent the periphery of the member 50 and may be supported by polepieces 52 and 53 (see FIG. 1), which are in turn supported bynon-magnetic insulating member 85 mounted on vacuum advance cup 86 ofthe distributor. The breaker points are commonly supported in a similarway from the vacuum advance cup. The magnetic reeds 47 and 48 extendfrom the encapsulated reed device and 'iIJre mounted on the pole pieces52 and 53 as shown in The system which has been described operates toprovide high voltage firing pulses in response to actuation of the reedswitch in synchronism with operation of an internal combustion enginehaving a plurality of cylinders with a spark plug in each cylinder.Although an eight cylinder engine has been illustrated, it will beapparent that the ignition system can be used with an engine having anynumber of cylinders. The system can also be used for providing ignitionpulses in response to actuation of the reed switch which may beindependent of the engine operation, for use in a turbine or jet engine.

FIGS. 3, 4 and 5 shown an alternate form of the rotating magneticstructure. This structure includes a disc shaped magnet 90 (FIG. 4),which is magnetized in the axial direction, so that the upper surfaceprovides one polarity and the lower surface provides the other polarity.Pole plates 91 and 92 are secured to the two faces of the disc magnet90. The two pole plates 91 and 92 may be of identical configuration,with the teeth or projections 93 and 94 thereon opposing each other, andpositioned at angles of 45 with respect to each other. The teeththerefore provide discrete poles, with alternate poles being of oppositepolarity and equally spaced around the circumference of the structure.Pole pieces 95 and 96, generally similar to the pole pieces 52 and 53 ofFIG. 1, are positioned so that they are intermittently aligned with thepole teeth 93 and 94 as the magnetic structure rotates. The pole pieces95 and 96 may support an encapsulated reed switch 98, similar to theswitch 45 as previously described. The magnetic structure of FIGS. 3, 4and 5 may be easier to provide than that shown in FIGS. 1 and 2 as thepermanent magnet is a simple ring. The pole plates can be easilyconstructed or soft iron.

In the event that the spacing between the pole pieces is not sufiicientfor the reed switch which is to be used to be positioned horizontallytherebetween, or that it is preferable to mount the reed switch in avertical direction, the reed switch may be supported as shown in FIG. 6.The pole pieces 95 and 96 may be positioned as shown in FIG. 3. Thereeds 100 and 101 of the reed switch, which extend from the capsule,have portions shaped to engage the pole pieces. Alternatively, bracketsof magnetic material may be used to connect the reeds to the polepieces. Reeds 100 and 101 may be similar to the reeds 47 and 48 of FIG.1 and may be used in the circuit described in FIG. 1.

The ignition system described has been found to provide eifectiveoperation of internal combustion automotive engines, both for startingand at high speed. The sealed reed contacts carry small currents andhave long life. The magnetic structure used provides very rapidswitching action. The circuit is protected so that excessive currentcannot be applied to the contacts of the sealed reed contacts as thesystem starts operation, or due to poor grounding of transistor 41 (FIG.1).

I claim:

1. An ignition system for an internal combustion engine including incombination, an ignition coil for providing high voltage firing pulsesfor the internal combustion engine, semiconductor switching means havinga portion providing a conductive path and a control portion forselectively rendering said path conductive, means connecting saidconductive path portion of said semiconductor switching means in serieswith at least a part of said ignition coil across potential supplymeans, and control means connected to said control portion of saidsemiconductor switching means for controlling the conduction thereof,said control means including magnetic reed switch means and a magneticstructure for operating the same, said magnetic reed switch meansincluding first and second magnetic reed elements having portions withcontacts adapted to engage each other to complete a circuit therethroughand a sealed enclosure about said portions, said reed elements havingportions extending outside said enclosure, said magnetic structureincluding pole pieces connected to said portions of said magnetic reedelements extendingoutside said enclosure, and a rotor having a permanentmagnet and discrete magnetic poles with alternate poles being ofopposite polarity, said rotor being movable to align adjacent ones ofsaid poles thereof with said pole pieces and then displace said polesfrom said pole pieces, whereby the flux through said magnetic reedswitch means changes suddenly and reverses in polarity to provide rapidswitching action.

2. An ignition system for an internal combustion engine including incombination, an ignition coil for providing high voltage firing pulsesfor the internal combustion engine, semi-conductor switching meanshaving a portion providing a conductive path and a control portion forselectively rendering said path conductive, means connecting saidconductive path portion of said semiconductor switching means in serieswith at least a part of said ignition coil across potential supplymeans, and control means connected to said control portion of saidsemiconductor switching means for controlling the conduction thereof,said control means including switch means having first and secondmagnetic reeds with portions having contacts for closing a circuit and amagnetic structure for operating the same, said switch means includingan enclosure about said portions of said reeds having contacts and saidreeds having portions extending from said enclosure, said magneticstructure including a rotor having a permanent magnet and discretemagnetic poles with alternate poles being of opposite polarity, andfirst and second pole pieces connected respectively to said portions ofsaid first and second magnetic reeds extending outside said enclosureand supporting the same so that said reeds extend substantially parallelto the axis of said rotor, said rotor being movable to align adjacentones of said poles thereof with said pole pieces and then displace saidpoles from said pole pieces, whereby the flux through said magnetic reedswitch means changes suddenly and reverses in polarity to provide rapidswitching action.

3. An ignition system for an internal combustion engine including incombination, an ignition coil for providing high voltage firing pulsesfor the internal combustion engine, semi-conductor switching meanshaving a portion providing a conductive path, means connecting saidconductive path portion in series with at least a part of said ignitioncoil across potential supply means, said switching means including asemiconductor device having a collector portion connected to a referencepotential and a base portion connected to the potential supply means,and control means connected to said base portion of said semiconductordevice for controlling the conduction in said conductive path insynchronism with operation of the internal combustion engine, saidcontrol means including magnetic reed switch means and a magneticstructure for operating the same, said magnetic switch means includingfirst and second magnetic reed elements having portions with contactsadapted to engage each other to complete a circuit therethrough and anenclosure about said portions, said reed elements having portionsextending outside said enclosure, means including resistance connectingsaid reed switch means between said base portion and the referencepotential, with said resistance limiting the current flowing throughsaid reed switch means, said magnetic structure including pole piecescoupled to said portions of said magnetic reed elements extendingoutside said enclosure and a rotor having a permanent magnet anddiscrete magnetic poles with alternate poles being of opposite polarity,said rotor being movable to align adjacent ones of said poles thereofwith said pole pieces and then displace said poles from said polepieces, whereby the flux through said magnetic reed switch means changessuddenly and reverses polarity to provide rapid switching action.

4. An ignition system for an internal combustoin engine including incombintion, an ignition coil for providing high voltage firing pulsesfor the internal combustion engine, semi-conductor switching meanshaving a portion providing a conductive path, means connecting saidconductive path portionin series with at least a part of said ignitioncoil across potential supply means, said switch-- ing means including atransistor having a collector electrode connected to a referencepotential and a base electrode connected to the potential supply means,and control means connected to said base electrode of said transistorfor controlling the conduction in said conductive path, said controlmeans including magnetic reed switch means and a magnetic structure foroperating the same, said switch means including first and second reedelements having portions with contacts thereon for completing a circuittherethrough and a sealed enclosure about said portions, means includingresistance connecting said reed switch means betwen said base electrodeand the reference potential, with said resistance limiting the currentflowing through said reed switch means, said magnetic structureincluding a rotor having magnetic poles movable with respect to saidmagnetic reed switch means, whereby the flux through said magnetic reedswitch means changes to provide switching action.

OTHER REFERENCES Specifications for the Heathkit, Heath Company, June28, 1963. References Cited by the Exammer 1. C. Norris: DelcotronicTransistor Ignition System,

UNITED STATES PATENTS 5 Iuly1963.

3;; rlrognola- References Cited by the Applicant aynes. 2/1957 Mike 123148 UNITED STATES PATENTS 9/1959 Holthouse 123-148 10 2, 2 1947 C06et 1. 1/1963 Straub 123 -148 2,878,298 3/1959 Giacoletto. 5/1964 Vriens315--209 2,999,914 9/1961 Stanaway.

FOREIGN PATENTS MARK NEWMAN, Primary Examiner.

Great Britain. LAURENCE M. GOODRIDGE, Examiner.

1. AN IGNITION SYSTEM FOR AN INTERNAL COMBUSTION ENGINE INCLUDING INCOMBINTION, AN IGNITION COIL FOR PROVIDING HIGH VOLTAGE FIRING PULSESFOR THE INTERNAL COMBUSTION ENGINE, SEMICODUCTOR SWITCHING MEANS HAVINGA PORTION PROVDING A CONDUCTIVE PATH AND A CONTROL PORTION FORSELECTIVELY RENDERING SAID PATH CONDUCTIVE, MEANS CONNECTING SAIDCONDUCTIVE PATH PORTION OF SAID SEMICONDUCTOR SWITCHING MEANS IN SERIESWITH AT LEAST A PART OF SAID IGNITION COIL ACROSS POTENTIAL SUPPLYMEANS, AND CONTROL MEANS CONNECTED TO SAID CONTROL PORTION OF SAIDSEMICONDUCTOR SWITCHING MEANS FOR CONTOLLING THE CONDUCTION THEREOF,SAID CONTROL MEANS INCLUDING MAGNETIC REED SWITCH MEANS AND A MAGNETICSTRUCTURE FOR OPERATING THE SAME, SAID MAGNETIC REED SWITCH MEANSINCLUDING FIRST AND SECOND MAGNETIC REED ELEMENTS HAVING PORTIONS WITHCONTACTS ADAPTED TO ENGAGE EACH OTHER TO COMPLETE A CIRCUIT THERETHROUGHAND A SEALED ENCLOSURE ABOUT SAID PORTIONS, SAID REED ELEMENTS HAVINGPORTION EXTENDING OUTSIDE SAID ENCLOSURE, SAID MAGNETIC STRCTUREINCLUDING POLE PIECES CONNECTED TO SAID PORTIONS OF SAID MAGNETIC REEDELEMENTS EXTENDING OUTSIDE SAID ENCLOSURE, AND A ROTOR HAVING APERMANENT MAGNET AND DISCRETE MAGNETIC POLES WITH ALTERNATE POLES BEINGOF OPPOSITE POLARTIY, SAID ROTOR BEING MOVABLE TO ALIGN ADJACENT ONES OFSAID POLES THEREOF WITH SAID POLE PIECES AND THEN DISPLACE SAID POLESFROM SAID POLE PIECES, WHEREBY THE FLUX THROUGH SAID MAGNETIC REEDSWITCH MEANS CHANGES SUDDENLY AND REVERSES IN POLARITY TO PROVIDE RAPIDSWITCHING ACTION.